This invention relates to communication circuit testing and more particularly to an improved apparatus and method for providing and detecting tone for troubleshooting and tracing communications cabling.
In working on telecommunications cabling, a typical function involves identifying or locating a specific cable among a number of cables. For example, it may be desired to locate a cable at a distant end thereof relative to a junction point. In accordance with the prior art, a toner locating system is employed wherein an audio tone generator is connected at one position on the cable, and a detector or tone probe is employed elsewhere along the cable to detect the tone in an attempt to identify and isolate the cable carrying the tone from among other cables. This isolation attempt can be taking place far away from the tone generator location.
Some practical problems arise in use of such toner systems. The toner locater system was originally employed in telephone communication systems but is now also employed in computer networking situations. However, for example, a 100 megabit per second computer network employs common mode terminations, and existing toner devices do not work because the common mode termination configuration attenuates the tone. This results in the signal being too weak due to the termination by network equipment and it becomes difficult to detect it at a remote location.
Also, sometimes in particular wiring situations, the audio signal applied to the cable by the tone generator is too strong and causes crosstalk and bleed into other wires on a given cable or into other cables, making it difficult to determine which cable is the actual cable to which the audio signal is being applied. Especially with a 1 Khz signal applied to CAT5 cables, the coupling is strong and at a distance from the tone generator the signal strength on two adjacent cables can be similar so as to make it difficult to determine which is the cable of interest. These issues can lead to wasted time, either mis-identifying cable due to bleed, or to not being able to locate the cable due to a weak signal.
A certain level of experience is needed to effectively use such a toner system and to listen for the correct tone, as fluorescent lighting equipment, CRTs and other equipment which is typically present in most commercial buildings, can induce signals onto cabling which is then detected by the tone probe.
A typical prior art toner system, illustrated with reference to FIG. 5, employs a 1 Khz high power square wave generator 110 which applies the audio signal to the cable 112 under test. The generator 110 typically has two states, on or off. Some generators may have a further option of selecting the frequency of the square wave from among 2 or 3 fixed frequencies. The generator is connected to the cable under test via 2 clip leads 113 which allow connection to an individual wire or via a network connector 115. A hand held tone sensor probe 114, is a an amplifier, includes a sensor tip 116 and a speaker 118, and detects and converts the square wave to an audible 1 Khz tone (or tone of whatever the frequency is of the applied signal) audible through the speaker. The configuration of the toner probe can also result in feedback, since the tone probe tip will normally be highly sensitive and can detect and feedback signal from the speaker on the tone probe.
In use, the prior art tone generator is manually connected to the cable under test and is turned on, and the technician then takes the probe to the remote location, which can be far away, on a different floor in a building, for example. It can be that after setting the tone generator and moving to the remote location, the technician realizes that a different configuration may be required. For example, the technician may now wish to use two wires of a twisted pair in a cat5 cable as a single conductor to provider a stronger radiating signal on the cable, by connecting the tone generator appropriately. However, since the tone generator is far away, the technician must now travel back to the generator site and adjust the connection, then returning to the remote cable test site, consuming time.